Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 220431

Area Forecast Discussion
National Weather Service Marquette MI
1131 PM EST Sun Jan 21 2018

.SHORT TERM...(This evening through Monday)
Issued at 414 PM EST SUN JAN 21 2018

...Winter storm with heavy snow and some ice begins on Monday...

Prime attention is on incoming winter storm which will arrive in
earnest over Upper Michigan by Monday afternoon/evening. All not
completely quiet in the near term tonight with low-level moisture
behind cold front over northern Upper Michigan leading to possible
freezing drizzle tonight and maybe into Monday morning over the
north central. Main messaging is on the winter storm but will need
to keep monitoring freezing drizzle potential as most roads are now
clear of snow thanks to recent warm up. Icy spots could develop as
temps tonight fall back into the 20s. Could also see more fog (and
this could lead to icy conditions as well) as has been observed near
Lk Superior northwest and north central today.

Expect the upper low over the high plains to move to eastern Kansas
by 12z while sfc low moves to northwest MO to the north of Kansas
City. Slower trend that showed up a couple days ago is still the way
to go. Peak of strength of upper low and associated dynamics will
still be southwest of Upper Michigan per H5 heights and deep layer q-
vector convergence. Swath of widespread precip will still spread
from south to north across Upper Michigan through the day. Area of
deformation should also expand into central Upper Michigan more into
Monday night as the upper low rumbles east. Speaking of rumbles,
will have to watch possible thunderstorms over MO into IA tonight as
they could at least partially disrupt initial warm air advection
precip late tonight and Monday morning into southern tier. This is
probably a partial reason for why models slowed down precip into
Upper Michigan on Monday. Eventually associated sfc low tracks to
Chicago vcnty late Monday aftn and toward northern Lower Michigan by
daybreak on Tuesday. Widespread snow will affect all of Upper
Michigan though there is still a sharp western edge to deeper
moisture (shown by RH at temps of -10c) and that could lead to more
freezing drizzle/freezing rain issues over far west as there just
may not be enough cloud ice to lead to snow as main pytpe. Tried to
message this as best could with lower snow amounts of 2-4/3-5 inches
from Gogebic to Keweenaw counties and more of a mention of freezing
precip. Elsewhere the only area that could see mix of freezing
drizzle and snow (again due to limited deep moisture for a time)
would be scntrl into east forecast area Mon aftn into Mon evening.

Total snow amounts synoptically from the system should end up
checking of at least 6" most areas. Good confidence that deformation
enhancement to over central will push most areas from Iron and
Dickinson counties into Baraga and Marquette counties more toward of
at least 8 inches. Highest amounts over a foot are likely to occur
in higher terrain of ncntrl with northeast winds adding upslope
enhancement. Snow will be very wet and heavy, especially compared to
what we have seen not only this cold season but also more recent
cold seasons. SLRs should generally be in the 10-13:1 range during
peak of synoptic snow. The wet snow will be difficult to shovel and
plow and drive in. All of these points were hit up in our messaging
in the WSW statement, on social media and in the briefing sent to
partners. Winter storm warnings were issued for all areas expect the
Keweenaw where lack of precip and cloud ice were factors. Even if
system ends up pulling a bit farther west, still seems that heaviest
snow would still remain east so think the advisory will work out
okay for now. Gogebic was a little tricky but with mixed precip over
western portions and possibility for heavy snow over eastern
sections (near Watersmeet) thought it was prudent to put them into a
warning as well. Blowing snow will eventually become an issue but
probably not until late Monday night near Lk Superior. More on those
hazards in the long term discussion.

.LONG TERM...(Tuesday through Sunday)
Issued at 345 PM EST SUN JAN 21 2018

The main forecast concerns through the extended are the lingering
impacts from blowing/drifting snow and lingering lake
effect/enhanced snow as the main winter storm expected to impact the
region continues to track over Lake Huron and over into Canada, then
the focus transitions to another system progged to track across the
Upper Mississippi and Great Lakes region this weekend.

Tuesday: As the main system continues to exit the region, forecast
soundings show deeper moisture beginning to vacate from west to
east. Given the shallow nature of the cold air and the marginal
support for ice based on the 850mb temperatures, it certainly is in
the realm of possibilities we could see precipitation switch over to
freezing drizzle. However, with forecast soundings still showing
colder temperatures around 900mb supportive of ice, opted to leave
out mentions of freezing drizzle for now. Lingering gusty northerly
winds will likely cause area of blowing and drifting snow, along
with reduced visibilities especially across the north central where
light snow will continue. Due to the lingering impacts, upon
collaboration with the short-term forecaster the consensus was to
run the winter storm warning through Tuesday morning across the
north central to take into account these lingering impacts. By
Tuesday evening, any lingering precipitation near Lake Superior will
quickly diminish as upper-level ridging and drier air work into the
region. Temperatures during the day will only climb into the teens
and lower 20s, so the combination of colder temperatures and gusty
northerly winds will make for a blustery day as apparent
temperatures drop down into the single digits for much of the area.

Wednesday through Friday: We could see a brief return of lake effect
snow showers out west towards the middle of the work week as a weak
shortwave tracks eastward across the Great Lakes region. Otherwise
high pressure will dominate as upper-level ridging builds across the
central CONUS, ahead of another vigorous trough beginning to dig
into the western CONUS. Return flow is expected to overspread Upper
Michigan through the end of the week as the main upper-level ridge
axis shifts eastward, allowing temperatures to climb into the 30s
and 40s by Friday!

As the aforementioned longwave trough tracks across the Rockies and
central CONUS towards the end of the week, this will favor the
development of a lee cyclone. With the more pronounced lift and
850mb warm air advection aimed across the Upper Mississippi Valley,
expect the surface low to track northeast towards western Lake
Superior by late Friday night. This will favor the development of
widespread rain/snow showers late Friday night.

Next Weekend: The medium range models have been consistent with
Upper Michigan remaining on the warm side of this next system
through a good portion of the day on Saturday. Therefore, any
precipitation that lingers across the area during the day will
likely fall as rain. Saturday will be another day with above normal
temperatures for this time of year, as highs climb into the upper
30s and lower 40s.

As the main trough axis pushes across the area and cold air
advection returns on the back side of the system, expect the rain to
transition over to snow from west to east Saturday evening into
early Sunday. This will allow temperatures to rapidly transition
from the mild pre-frontal air mass to the cold post-frontal air mass
Saturday night into Sunday. Given the cold air advection behind the
system, expect lake effect snow to impact areas downwind of Lake
Superior on Sunday, along with the return of near normal

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1131 PM EST SUN JAN 21 2018

Tricky forecast continues with plenty of low level moisture from
snow melt today along with upslope northeast winds behind a cold
front. This will bring VLIFR/LIFR conditions for this forecast
period with fog and/or low clouds. Will be some freezing drizzle as
well. Snow with incoming winter storm should start up at SAW by
midday on Monday and will get heavy by late afternoon.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 345 PM EST SUN JAN 21 2018

Winds will increase to 25 to 30 knots tonight through early Monday
morning, and will further increase to gales of 35 to 40 knots Monday
into Tuesday. Tuesday winds will remain between 20 and 30 knots.
During the period of higher winds, expect heavy freezing spray to
develop as well. Wednesday through the day on Thursday, things will
quiet down across the lake as high pressure moves overhead and winds
remain below 20 knots. Later this week into next weekend, winds will
pick back up to around 25 to 30 knots, with gales possible towards
the end of the weekend, as another storm system tracks across the
Upper Great Lakes.

Upper Michigan...
  Winter Storm Warning from 7 AM EST /6 AM CST/ Monday to 1 AM EST
     /midnight CST/ Tuesday for MIZ002-009>012-084.

  Winter Storm Warning from 10 AM Monday to 6 AM EST Tuesday for

  Winter Weather Advisory from 1 PM Monday to 6 AM EST Tuesday for

  Winter Storm Warning from 10 AM Monday to 1 PM EST Tuesday for

Lake Superior...
  Heavy Freezing Spray Warning from 4 AM to 6 PM EST Tuesday for

  Gale Warning from 5 PM Monday to 10 AM EST Tuesday for

  Heavy Freezing Spray Warning from 10 PM Monday to 4 PM EST
     Tuesday for LSZ263-264.

  Gale Warning from 10 AM EST /9 AM CST/ Monday to 5 AM EST /4 AM
     CST/ Tuesday for LSZ162-263.

Lake Michigan...
  Gale Warning from 10 AM Monday to 4 AM EST Tuesday for LMZ248-



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